Periódicos Brasileiros em Medicina Veterinária e Zootecnia

Zinc sulphate turbidity as a screening test of passive transfer of immunity in newborn foals

Pompermayer, EndrigoDe La Côrte, Flávio DesessardsRubin, Mara Iolanda Batistella

Background: Passive immunity acquired by colostrum ingestion is essential to prevent neonatal infections. Failure ofpassive transfer (FPT) of maternal immunity occurs in foals that fail to absorb enough immunoglobulins within 24 h afterbirth. Foals with FPT are at increased risk of infections and death. Serum samples from neonatal foals might be examinedfor FPT using the zinc sulphate turbidity (ZST) test. The aim of this study was to investigate the accuracy of the ZST test,performed at two different times after first suckling (12 and 18 h), to detect FPT in newborn foals. The effect of temperatureon the turbidity intensity resulting from the ZST reaction was also investigated.Materials, Methods & Results: Blood samples were collected from 112 newborn foals at 12 h after the first colostrumintake. In 36 foals, additional serum samples were collected at 18 h after first colostrum intake. The serum samples weretested with the ZST test and, later, in the laboratory setting, the ZST test was repeated. The IgG levels were measured bysingle radial immunodiffusion (SRID), which was used as the reference method. The standard solution used for the interpretation of results had a turbidity corresponding to approximately 800 mg/dL of immunoglobulins (IgG). The mean IgG concentration measured at 12 and 18 h after the first colostrum intake was analyzed using the t-test for paired samples.Values of absorbance of ZST test under different temperatures were analyzed using a one-way analysis of variance, andmeans were compared using the Tukey test. The relationship between the temperature of the solution and absorbance wasdetermined using the Pearson’s correlation coefficient. Based on SRID results, 12 foals (10.7%) had serum IgG concentration < 400 mg and 26 foals (23.2%) had IgG levels between 400 and 800 mg/dL. Serum levels of IgG determined bySRID in 36 foals were similar (P > 0.05) between 12 h (943.9 ± 508.6 mg/dL) and 18 h (975.9 ± 525.6 mg/dL)...(AU)

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